Wellness/functional beverages are becoming the fastest growing beverage segment in the U.S. (Miller, G., Healthy growth ahead for wellness drinks, Food Technology 10: 21-24 (2005)). In particular, the sports/energy drink category was reported to have grown 10% in 2003/2004 and was one of the fastest growing food and beverage categories worldwide (Nielson, A. C., What's hot around the globe: Insights on growth in food and beverages 2004, ACNielson Global Services: 1-39 (2004)). In general, high protein sports drinks make up a considerable portion of this growing drink market with whey proteins being the major protein ingredient in these drinks. Much has been learned lately about the role of proteins in improving health. By reducing consumption of carbohydrates and increasing consumption of protein, individuals might benefit by losing weight, controlling diabetes, losing fat and building muscle.
Whey proteins have a high nutritive value, due in part at least to the compositional profile of the proteins that includes a balanced array of amino acids. As a result, whey proteins are recognized as a premier protein source, particularly for individuals who are health-conscious and have specific dietary needs, such as athletes and body builders. Generally, it is desirable to provide as much protein as possible from whey proteins. However, as the whey protein content is increased and mineral salts are added, nutritional liquid compositions or beverages, such as sports nutrition beverages, suffer from problems.
For instance, the optical clarity of whey protein containing beverages can be maintained at pH ≦3.5 and low levels of salts (generally lower than 30 mM), but even under these conditions, once the protein concentration increases to between 3 and 5%, a significant level of astringency is detected. Neutral pH drinks do not have the astringency problem but whey proteins form large aggregates that may phase separate or gel. This is prevented by using mixtures of whey or other milk proteins; however, the drinks are opaque.
Properties that can be considered detrimental to the quality of protein beverages include loss of clarity (increased turbidity or opacity or the presence of an undesirable pigment), elevated viscosity, phase separation, elevated level of astringency and undesirable flavor and/or aroma. The majority of these defects involve heat-induced changes in the proteins. Thus, the high temperatures used for pasteurization and ultra high temperature sterilization in conventional beverage processing can be problematic. In conventional beverage processing, the raw materials are prepared and mixed before they are heated and cooled. Whey proteins become cloudy and/or precipitate when subjected to these elevated temperatures. In addition, whey proteins at neutral pH and in the presence of mineral salts, such as calcium, will aggregate after being heated which results in a turbid appearance and/or gelation thus limiting the potential market of high protein drinks with calcium supplement.
Thermal stability of proteins is a general term that describes the ability of a protein solution to survive a thermal process without detrimental changes. There has been considerable interest in the development of high protein drinks containing mineral salts at neutral pH, which remain stable after heat processing. Success in developing such whey protein products or processes will certainly benefit the dairy and beverage industries.
Accordingly, the present invention discloses a process of making thermally stable whey proteins for high protein beverages containing mineral salts at a neutral pH, which can be used not only in making high-protein beverages containing mineral salts at a neutral pH, but also in other liquid and semi-solid applications which require heat stable whey proteins, such as soups, sauces, gravies and syrups.